Bluetooth technology (BT) and its low power derivative Bluetooth Low Energy (BLE) are being used for the secure detection of the proximity of portable devices as part of user authentication and presence detection schemes, including multi-factor authentication schemes. Such BT/BLE solutions are performed using received signal strength indication (RSSI) measurements for device discovery and for affirming the location of the devices. This method is inaccurate and may have error margins on the order of a few meters. In addition, such schemes are susceptible to various remote spoofing attacks and may not be suitable for high security use cases.